Senile dementia of the Alzheimer type (SDAT), the major cause of dementia among the elderly, is a growing health problem. Although much has been learned about the pathophysiology of this disease, little is known about etiological factors. We propose to seek information about specific genetic, environmental, and metabolic risk factors by carrying out a cross-cultural case control study of SDAT. We will utilize an epidemiological interview together with studies of serum haptoglobins as linked genetic markers; immunological changes manifested by lymphocyte responses and serum immunoglobulins; serum antibodies to choline acetyltransferase, and parathormone status. One aspect of the social impact of SDAT will be studied by investigating techniques adopted by families for coping with an afflicted family member.